Automatic pump chamber control adjustment

ABSTRACT

A method and system for lifting drilling mud from subsea to a drilling vessel, which uses a pump having a body with a chamber, and a bladder in the chamber. The bladder attaches to the body and defines water and mud sides in the chamber. A mud inlet valve allows mud into the mud side of the chamber; which moves the bladder into the water side and urges water in the water side from the chamber and through a water exit valve. Pressurized water enters the chamber through a water inlet valve, which in turn pushes the bladder and mud from the chamber through a mud exit valve. The bladder separates the mud and water as it reciprocates in the chamber. The travel of the bladder in the chamber is controlled to prevent damage from contact with the chamber.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to and the benefit of co-pending U.S.Provisional Application Ser. No. 61/791,258, filed Mar. 15, 2013, thefull disclosure of which is hereby incorporated by reference herein forall purposes.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present disclosure relates in general to a system and method formaintaining volume in a bladder pump at the end of each pump stroke.

2. Description of Prior Art

Subsea drilling systems typically employ a vessel at the sea surface, ariser connecting the vessel with a wellhead housing on the seafloor, anda drill string. A drill bit is attached on a lower end of the drillstring, and used for excavating a borehole through the formation belowthe seafloor. The drill string is suspended subsea from the vessel intothe riser, and is protected from seawater while inside of the riser.Past the lower end of the riser, the drill string inserts through thewellhead housing just above where it contacts the formation. Generally,a rotary table or top drive is provided on the vessel for rotating thestring and bit. Drilling mud is usually pumped under pressure into thedrill string, and is discharged from nozzles in the drill bit. Thedrilling mud, through its density and pressure, controls pressure in thewell and cools the bit. The mud also removes formation cuttings from thewell as it is circulated back to the vessel. Traditionally, the mudexiting the well is routed through an annulus between the drill stringand riser. However, as well control depends at least in part on thecolumn of fluid in the riser, the effects of corrective action inresponse to a well kick or other anomaly can be delayed.

Fluid lift systems have been deployed subsea for pressurizing thedrilling mud exiting the wellbore. Piping systems outside of the risercarry the mud pressurized by the subsea lift systems. The lift systemsinclude pumps disposed proximate the wellhead, which reduce the time forwell control actions to take effect.

SUMMARY OF THE INVENTION

A method and system for lifting drilling mud from subsea to a drillingvessel. Drilling mud exiting a wellbore is directed to a subsea pumpthat includes a body, a chamber in the body, and a bladder in thechamber. An outer periphery of the bladder sealingly attaches to thebody, and defines a water side and a mud side in the chamber. A mudinlet valve selectively opens to allow mud to flow into the mud side ofthe chamber. As mud enters the chamber, the bladder is moved into thewater side, and urges water in the water side from the chamber andthrough a selectively opened water exit valve. Pressurized water entersthe chamber through a selectively opened water inlet valve, which inturn exerts a force against the bladder that urges the mud from thechamber through a selectively opened mud exit valve. The bladdermaintains a barrier between the mud and water as it reciprocates in thechamber. The travel of the bladder in the chamber is controlled toprevent damage from contact with the chamber.

BRIEF DESCRIPTION OF DRAWINGS

Some of the features and benefits of the present invention having beenstated, others will become apparent as the description proceeds whentaken in conjunction with the accompanying drawings, in which:

FIG. 1 is a side sectional view of an example of a subsea drillingsystem in accordance with the present invention.

FIGS. 2 and 3 are partial side sectional views of an example of a subseapump for use with the drilling system of FIG. 1 in different pumpingmodes and in accordance with the present invention.

FIG. 4 is a side view of an embodiment of a subsea drilling system witha riser and pump kit, and in accordance with an embodiment of theinvention.

While the invention will be described in connection with the preferredembodiments, it will be understood that it is not intended to limit theinvention to that embodiment. On the contrary, it is intended to coverall alternatives, modifications, and equivalents, as may be includedwithin the spirit and scope of the invention as defined by the appendedclaims.

DETAILED DESCRIPTION OF INVENTION

The method and system of the present disclosure will now be describedmore fully hereinafter with reference to the accompanying drawings inwhich embodiments are shown. The method and system of the presentdisclosure may be in many different forms and should not be construed aslimited to the illustrated embodiments set forth herein; rather, theseembodiments are provided so that this disclosure will be thorough andcomplete, and will fully convey its scope to those skilled in the art.Like numbers refer to like elements throughout.

It is to be further understood that the scope of the present disclosureis not limited to the exact details of construction, operation, exactmaterials, or embodiments shown and described, as modifications andequivalents will be apparent to one skilled in the art. In the drawingsand specification, there have been disclosed illustrative embodimentsand, although specific terms are employed, they are used in a genericand descriptive sense only and not for the purpose of limitation.

Shown in FIG. 1 is a side partial sectional view of an exampleembodiment of a drilling system 10 for forming a wellbore 12 subsea. Thewellbore 12 intersects a formation 14 that lies beneath the sea floor16. The wellbore 12 is formed by a rotating bit 18 coupled on an end ofa drill string 20 shown extending subsea from a vessel 22 floating onthe sea surface 24. The drill string 20 is isolated from seawater by anannular riser 26; whose upper end connects to the vessel 22 and lowerend attaches onto a blowout preventer (BOP) 28. The BOP 28 mounts onto awellhead housing 30 that is set into the sea floor 16 over the wellbore12. A mud return line 32 is shown having an end connected to the riser26 above BOP 28, which routes drilling mud exiting the wellbore 12 to alift pump assembly 34 schematically illustrated subsea. Within the liftpump assembly 34, drilling mud is pressurized for delivery back to thevessel 22 via mud return line 36.

FIG. 2 includes a side sectional view of an example of a pump 38 for usewith lift pump assembly 34 (FIG. 1). Pump 38 includes a generally hollowand elliptically shaped pump housing 40. Other shapes for the housing 40include circular and rectangular, to name a few. An embodiment of aflexible bladder 42 is shown within the housing 40; which partitions thespace within the housing 40 to define a mud space 44 on one side of thebladder 42, and a water space 46 on an opposing side of bladder 42. Aswill be described in more detail below, bladder 42 provides a sealingbarrier between mud space 44 and water space 46. In the example of FIG.2, bladder 42 has a generally elliptical shape and an upper open space48 formed through a side wall. Upper open space 48 is shown coaxiallyregistered with an opening 50 formed through a side wall of pump housing40. A disk-like cap 52 bolts onto opening 50, where cap 52 has anaxially downward depending lip 53 that coaxially inserts within opening50 and upper open space 48. A portion of the bladder 42 adjacent itsupper open space 48 is wedged between lip 53 and opening 50 to form asealing surface between bladder 42 and pump housing 40.

A lower open space 54 is formed on a lower end of bladder 42 distal fromupper open space 48, which in the example of FIG. 2 is coaxial withupper open space 48. An elliptical bumper 56 is shown coaxially set inthe lower open space 54. The bumper 56 includes upper and lower segments58, 60 coupled together in a clamshell like arrangement, and thatrespectively seal against upper and lower radial surfaces on the loweropen space 54. The combination of sealing engagement of cap 52 andbumper 56 with upper and lower open spaces 42, 54 of bladder 42,effectively define a flow barrier across the opposing surfaces ofbladder 42. Further shown in the example of FIG. 2 is an axial rod 62that attaches coaxially to upper segment 56 and extends axially awayfrom lower segment 58 and through opening 50.

Still referring to FIG. 2, a mud line 64 is shown having an inlet endconnected to mud return line 32, and an exit end connected with mudreturn line 36. A mud inlet valve 66 in mud line 64 provides selectivefluid communication from mud return line 32 to a mud lead line 68 shownbranching from mud line 64. Lead line 68 attaches to an annularconnector 70, which in the illustrated example is bolted onto housing40. Connector 70 mounts coaxially over an opening 72 shown formedthrough a sidewall of housing 40 and allows communication between mudspace 44 and mud line 64 through lead line 68. A mud exit valve 74 isshown in mud line 64 and provides selective communication between mudline 64 and mud return line 36.

Water may be selectively delivered into water space 46 via a watersupply line 76 (FIG. 1) shown depending from vessel 22 and connecting tolift pump assembly 34. Referring back to FIG. 2, a water inlet lead line78 has an end coupled with water supply line 76 and an opposing endattached with a manifold assembly 80 that mounts onto cap 52. Theembodiment of the manifold assembly 80 of FIG. 2 includes a connector82, mounted onto a free end of a tubular manifold inlet 84, an annularbody 86, and a tubular manifold outlet 88, where the inlet and outlet84, 88 mount on opposing lateral sides of the body 86 and are in fluidcommunication with body 86. Connector 82 provides a connection point foran end of water inlet lead line 78 to manifold inlet 84 so that leadline 78 is in communication with body 86. A lower end of manifold body86 couples onto cap 52; the annulus of the manifold body 86 is in fluidcommunication with water space 46 through a hole in the cap 52 thatregisters with opening 50. An outlet connector 90 is provided on an endof manifold outlet 88 distal from manifold body 86, which has an endopposite its connection to manifold outlet 88 that is attached to awater outlet lead line 92. On an end opposite from connector 90, wateroutlet lead line 92 attaches to a water discharge line 94; that as shownin FIG. 1, may optionally provide a flow path directly subsea.

A water inlet valve 96 shown in water inlet lead line 78 providesselective water communication from vessel 22 (FIG. 1) to water space 46via water inlet lead line 78 and manifold assembly 80. A water outletvalve 98 shown in water outlet lead line 92 selectively providescommunication between water space 46 and water discharge line 94 throughmanifold assembly 80 and water outlet lead line 92.

In one example of operation of pump 38 of FIG. 2, mud inlet valve 66 isin an open configuration, so that mud in mud return line 32 communicatesinto mud line 64 and mud lead line 68 as indicated by arrow A_(Mi).Further in this example, mud exit valve 74 is in a closed positionthereby diverting mud flow into connector 70, through opening 72, andinto mud space 44. As illustrated by arrow A_(U), bladder 42 is urged ina direction away from opening 72 by the influx of mud, thereby impartinga force against water within water space 46. In the example, wateroutlet valve 98 is in an open position, so that water forced from waterspace 46 by bladder 42 can flow through manifold body 86 and manifoldoutlet 88 as illustrated by arrow A_(Wo). After exiting manifold outlet88, water is routed through water outlet lead line 92 and into waterdischarge line 94.

An example of pressurizing mud within mud space 44 is illustrated inFIG. 3, wherein valves 66, 98 are in a closed position and valves 96, 74are in an open position. In this example, pressurized water from watersupply line 76 is free to enter manifold assembly 80 where asillustrated by arrow A_(Wi), the water is diverted through opening 50and into water space 46. Introducing pressurized water into water space46 urges bladder 42 in a direction shown by arrow A_(D). Pressurizedwater in the water space 46 urges bladder 42 against the mud, whichpressurizes mud in mud space 44 and directs it through opening 72. Afterexiting opening 72, the pressurized mud flows into lead 68, where it isdiverted to mud return line 36 through open mud exit valve 74 asillustrated by arrow A_(Mo). Thus, providing water at a designatedpressure into water supply line 76 can sufficiently pressurize mudwithin mud return line 36 to force mud to flow back to vessel 22 (FIG.1).

As illustrated in FIGS. 2 and 3, bumper 56 travels axially withinhousing 40, and has end strokes proximate to the inner surface ofhousing 40. An optional controller 100 (FIG. 1) may be provided forlimiting travel of bladder 42 and bumper 56 to avoid collisions ofbladder 42 or bumper 56 with the inner surface of housing 40. In anembodiment, controller 100 includes an information handling system, andreceives or contains instructions to selectively operate valves 66, 74,78, 98. Optionally, valves 66, 74, 78, 98 can include actuators (notshown) in communication with and/or controlled by controller 100, thatmanipulate the valves 66, 74, 78, 98 to limit travel of the bumper 56.The controller 100 can be set based upon an increase or decrease in fillvolume that alters velocity of flow in one of the chambers 44, 46. Userdefined set points can be input to the controller 100 for establishinglimits of travel of the bladder 42. This can be manifested via controlof the valves 66, 74, 96, 98 so that they open and close at designatedtimes and sequences so that travel of bladder 42 and/or bumper 56prevents or avoids collision with housing 40. Moreover, a set bias maybe included with commands in the controller so that the control systemautomatically adjusts the set points to a higher or lower value to bringbladder travel within a safe range and thereby avoid any damagingcontact. Examples exist wherein volume in one of the chambers 44, 46 ata maximum stroke ranges from about 15 gallons to about 55 gallons. Bysetting the set points with an included bias, the set points areadjusted during use so that in a subsequent cycle of pumping, the extentof bladder travel is decreased to avoid any overshoot from a designatedposition.

Referring now to FIG. 4, an alternate embodiment of drilling system 10Ais shown in side partial sectional view and wherein lift pump assembly34A includes a mud pump kit 102 mounted integral onto riser 26A. In thisexample, mud pump kit 102 includes a subsea module 104 showncircumscribing riser 26A and that includes mud distribution manifold(not shown) and other flow control devices for selectively divertingflow to desired destinations. A riser module 106 is illustrated mountedon an upper surface of subsea module 104, which also circumscribes riser26A. Riser module 106 of FIG. 4 includes hydraulic power units forpressurizing hydraulic fluid that in an example is used for actuatingdevices subsea. Riser module 106 also includes hydraulic control systemsconnection hardware for mounting mud pump kit 102 to riser 26A. Pumps 38(FIG. 2) are housed in pump modules 108, 110 shown set on riser module106. In an embodiment, pump modules 108, 110 each include three pumps38. A solids recovery unit (SRU) 112 is shown above the pump modules108, 110, and a subsea rotating device (SRD) 114 attaches to an upperend of SRU 112. An upper end of SRD 114 flangedly attaches to a riserjoint 116, where in one example a substantial portion of the riser 26Abetween SRD 114 and vessel 22 (FIG. 1) is made up of stacked riserjoints 116.

In the example of FIG. 4, mud exiting drill string 20 flows upward in anannulus 118 defined between drill string 20 and wellbore 12, and whichextends further upward between drill string 20 and riser 26A. The mudflows past mud pump kit 102 and SRU 112 within annulus 118 and into SRD114 where a packer (not shown) blocks the mud. In an embodiment, theannulus 118 above packer is filled with sea water or other fluid. Mudwithin annulus 118 below packer is diverted to SRU 112 where cuttings orother solids are removed or particulated. After being processed in theSRU 112, the mud is directed to the pump modules 108, 110 where it ispressurized so it can flow back to vessel 22. Processing the mud in theSRU 112 can prevent damage to the pumps 38 (FIG. 2) in the modules 108,110.

In an example, modules 104, 106, 108, 110 are modular elements that canbe transported separately to the vessel 22 (FIG. 1) on site, where thepump kit 102 is assembled. A significant time savings is one advantageof the modularity of modules 104, 106, 108, 110. Because loading a fullyassembled pump kit 102 onto a vessel 102 causes such an asymmetricweight distribution that requires anchoring and stabilization, which isunachievable on site. Whereas the vessel 22 can accommodate individualmodules 104, 106, 108, 110 on site and without becoming unstable. Pumpmodules 108, 110 are individually detachable from the pump kit 102, andthus further enhancing modularity of the pumping system. Dedicatedpiping (not shown) is routed from SRU 112 and separately to each module108, 110 so that one of the modules 108, 110 can remain operationalwhile the other is removed or otherwise out of service. Further, sparemodules can be kept on site for one or both modules 108, 110, and caninstalled in place of a one of the modules 108, 110 with little or nostoppage of operation of pumping mud to the vessel 22.

In an alternate embodiment, BOP 28A is a BOP stack, whose upper portionincludes an annular blowout preventer and is part of a lower marineriser package (LMRP). Additionally, LMRP can include controls, amultiplexer unit, and pods. In an embodiment, modules 104, 106, 108,110, SRU 112, SRD 114, BOP 28A, and riser joints 116 are delivered tothe vessel 22 (FIG. 1) while on site and disposed above wellbore 12.While on the vessel 22, modules 104, 106, 108, 110 are attached togetherto form mud pump kit 102 which is coupled with BOP 28A. SRU 112 and SRD114 are attached onto mud pump kit 102; while suspended from riserjoints 116 the assembled unit is lowered subsea onto wellhead housing30.

The present invention described herein, therefore, is well adapted tocarry out the objects and attain the ends and advantages mentioned, aswell as others inherent therein. While a presently preferred embodimentof the invention has been given for purposes of disclosure, numerouschanges exist in the details of procedures for accomplishing the desiredresults. These and other similar modifications will readily suggestthemselves to those skilled in the art, and are intended to beencompassed within the spirit of the present invention disclosed hereinand the scope of the appended claims.

What is claimed is:
 1. A mud lift pump for lifting drilling mud from asubsea wellbore comprising: a housing; a water space in the housing; amud space in the housing that is in pressure communication with thewater space; a bladder mounted in the housing having a side in contactwith the water space and an opposing side in contact with the mud space,and that defines a barrier between the water and mud space; and acontroller for limiting a travel of the bladder within the chamber. 2.The mud lift pump of claim 1, further comprising: a water inlet havingan entrance in selective communication with a source of pressurizedwater, and an exit in communication with the water space; a waterdischarge having an entrance in communication with the water space, andan exit in selective communication with a water effluent line; a mudinlet having an entrance in selective communication with drilling mudfrom a subsea well an exit in communication with the mud space; and amud discharge having an entrance in communication with the mud space,and an exit in selective communication with a lift line that connects toa drilling vessel.
 3. A method of pumping mud from a subsea wellborecomprising: providing a pump comprising, a housing, a water space in thehousing, a mud space in the housing that is in pressure communicationwith the water space, and a bladder mounted in the housing having a sidein contact with the water space and an opposing side in contact with themud space, and that defines a flow barrier between the water and mudspace; and controlling movement of the bladder within the chamber, sothat the bladder avoids contact with the housing.